In one example of known liquid delivery apparatuses, a cylinder containing a plunger inserted therein in a reciprocally movable manner is communicated with a suction valve and a discharge valve. In that type of apparatus, when the plunger is reciprocally moved, the suction valve is opened and a liquid is supplied to the cylinder in a retraction stroke of the plunger, while the discharge valve is opened and the liquid is discharged from the cylinder in an advance stroke of the plunger, whereby the liquid is delivered from a nozzle communicated with the discharge valve (Patent Document 1).
In another example of known liquid delivery apparatuses, a suction port and a discharge port are selectively communicated with a cylinder containing a plunger inserted therein by a selector valve, which has a valve member rotated in a valve chamber, such that the communication between the suction port and the cylinder and the communication between the discharge port and the cylinder are changed over from one to the other (Patent Document 2).
Patent Document 1: Japanese Patent Laid-Open No. 58-178888
Patent Document 2: Japanese Patent Laid-Open No. 60-19970